Occlusion detection system and method

ABSTRACT

A method, computer program product, and infusion pump assembly for determining a first rate-of-change force reading that corresponds to the delivery of a first dose of an infusible fluid via an infusion pump assembly. At least a second rate-of-change force reading is determined that corresponds to the delivery of at least a second dose of the infusible fluid via the infusion pump assembly. An average rate-of-change force reading is determined based, at least in part upon the first rate-of-change force reading and the at least a second rate-of-change force reading.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/414,940, filed May 17, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/851,906, filed Dec. 22, 2017, which is acontinuation of U.S. patent application Ser. No. 14/703,473, filed May4, 2015, which is a continuation of U.S. patent application Ser. No.13/549,962, filed on Jul. 16, 2012, now U.S. Pat. No. 9,024,768, whichis a continuation of U.S. patent application Ser. No. 12/249,621, filedOct. 10, 2008, now U.S. Pat. No. 8,223,028, each of which is herebyincorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to occlusion detection and, more particularly,to occlusion detection within infusion pump assemblies.

BACKGROUND

An infusion pump assembly may be used to infuse a fluid (e.g., amedication or nutrient) into a user. The fluid may be infusedintravenously (i.e., into a vein), subcutaneously (i.e., into the skin),arterially (i.e., into an artery), and epidurally (i.e., into theepidural space).

Infusion pump assemblies may administer fluids in ways that would beimpractically expensive/unreliable if performed manually by nursingstaff. For example, an infusion pump assembly may repeatedly administersmall quantities of an infusible fluid (e.g., 0.1 mL per hour), whileallowing the user to request one-time larger “bolus” doses.

Unfortunately, occlusions may occur that may impede/prevent the deliveryof the infusible fluid, which may result in medical complications forthe user.

SUMMARY OF DISCLOSURE

In a first implementation, a method includes determining a firstrate-of-change force reading that corresponds to the delivery of a firstdose of an infusible fluid via an infusion pump assembly. At least asecond rate-of-change force reading is determined that corresponds tothe delivery of at least a second dose of the infusible fluid via theinfusion pump assembly. An average rate-of-change force reading isdetermined based, at least in part, upon the first rate-of-change forcereading and the at least a second rate-of-change force reading.

One or more of the following features may be included. The averagerate-of-change force reading may be compared to a thresholdrate-of-change force reading to determine if the average rate-of-changeforce reading exceeds the threshold rate-of-change force reading. If theaverage rate-of-change force reading exceeds the thresholdrate-of-change force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the first rate-of-change force reading may includedetermining a first initial force reading prior to dispensing the firstdose of the infusible fluid. The first dose of the infusible fluid maybe dispensed. A first final force reading may be determined subsequentto dispensing the first dose of the infusible fluid. The firstrate-of-change force reading may be determined based, at least in part,upon the first initial force reading and the first final force reading.

One or more of the first initial force reading and the first final forcereading may be compared to a threshold force reading to determine if oneor more of the first initial force reading and the first final forcereading exceeds the threshold force reading. If one or more of the firstinitial force reading and the first final force reading exceeds thethreshold force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the at least a second rate-of-change force reading mayinclude determining at least a second initial force reading prior todispensing the at least a second dose of the infusible fluid. The atleast a second dose of the infusible fluid may be dispensed. At least asecond final force reading may be determined subsequent to dispensingthe at least a second dose of the infusible fluid. The at least a secondrate-of-change force reading may be determined based, at least in part,upon the at least a second initial force reading and the at least asecond final force reading.

The infusion pump assembly may include a battery assembly configured topower the infusion pump assembly. An actual voltage level of the batteryassembly may be compared to a minimum voltage requirement to determineif the actual voltage level meets the minimum voltage requirement. Ifthe actual voltage level does not meet the minimum voltage requirement,an alarm sequence may be initiated on the infusion pump assembly.

One or more displaceable mechanical components included within theinfusion pump assembly may be monitored to determine if the one or moredisplaceable mechanical components were displaced an expecteddisplacement in response to delivery of one or more of the first dose ofthe infusible fluid and the second dose of the infusible fluid. If theone or more displaceable mechanical components were not displaced theexpected displacement in response to delivery of one or more of thefirst dose of the infusible fluid and the second dose of the infusiblefluid, an alarm sequence may be initiated on the infusion pump assembly.

In another implementation, a computer program product resides on acomputer readable medium that has a plurality of instructions stored onit. When executed by a processor, the instructions cause the processorto perform operations including determining a first rate-of-change forcereading that corresponds to the delivery of a first dose of an infusiblefluid via an infusion pump assembly. At least a second rate-of-changeforce reading is determined that corresponds to the delivery of at leasta second dose of the infusible fluid via the infusion pump assembly. Anaverage rate-of-change force reading is determined based, at least inpart, upon the first rate-of-change force reading and the at least asecond rate-of-change force reading.

One or more of the following features may be included. The averagerate-of-change force reading may be compared to a thresholdrate-of-change force reading to determine if the average rate-of-changeforce reading exceeds the threshold rate-of-change force reading. If theaverage rate-of-change force reading exceeds the thresholdrate-of-change force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the first rate-of-change force reading may includedetermining a first initial force reading prior to dispensing the firstdose of the infusible fluid. The first dose of the infusible fluid maybe dispensed. A first final force reading may be determined subsequentto dispensing the first dose of the infusible fluid. The firstrate-of-change force reading may be determined based, at least in part,upon the first initial force reading and the first final force reading.

One or more of the first initial force reading and the first final forcereading may be compared to a threshold force reading to determine if oneor more of the first initial force reading and the first final forcereading exceeds the threshold force reading. If one or more of the firstinitial force reading and the first final force reading exceeds thethreshold force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the at least a second rate-of-change force reading mayinclude determining at least a second initial force reading prior todispensing the at least a second dose of the infusible fluid. The atleast a second dose of the infusible fluid may be dispensed. At least asecond final force reading may be determined subsequent to dispensingthe at least a second dose of the infusible fluid. The at least a secondrate-of-change force reading may be determined based, at least in part,upon the at least a second initial force reading and the at least asecond final force reading.

The infusion pump assembly may include a battery assembly configured topower the infusion pump assembly. An actual voltage level of the batteryassembly may be compared to a minimum voltage requirement to determineif the actual voltage level meets the minimum voltage requirement. Ifthe actual voltage level does not meet the minimum voltage requirement,an alarm sequence may be initiated on the infusion pump assembly.

One or more displaceable mechanical components included within theinfusion pump assembly may be monitored to determine if the one or moredisplaceable mechanical components were displaced an expecteddisplacement in response to delivery of one or more of the first dose ofthe infusible fluid and the second dose of the infusible fluid. If theone or more displaceable mechanical components were not displaced theexpected displacement in response to delivery of one or more of thefirst dose of the infusible fluid and the second dose of the infusiblefluid, an alarm sequence may be initiated on the infusion pump assembly.

In another implementation, an infusion pump assembly is configured toperform operations including determining a first rate-of-change forcereading that corresponds to the delivery of a first dose of an infusiblefluid via an infusion pump assembly. At least a second rate-of-changeforce reading is determined that corresponds to the delivery of at leasta second dose of the infusible fluid via the infusion pump assembly. Anaverage rate-of-change force reading is determined based, at least inpart, upon the first rate-of-change force reading and the at least asecond rate-of-change force reading.

One or more of the following features may be included. The averagerate-of-change force reading may be compared to a thresholdrate-of-change force reading to determine if the average rate-of-changeforce reading exceeds the threshold rate-of-change force reading. If theaverage rate-of-change force reading exceeds the thresholdrate-of-change force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the first rate-of-change force reading may includedetermining a first initial force reading prior to dispensing the firstdose of the infusible fluid. The first dose of the infusible fluid maybe dispensed. A first final force reading may be determined subsequentto dispensing the first dose of the infusible fluid. The firstrate-of-change force reading may be determined based, at least in part,upon the first initial force reading and the first final force reading.

One or more of the first initial force reading and the first final forcereading may be compared to a threshold force reading to determine if oneor more of the first initial force reading and the first final forcereading exceeds the threshold force reading. If one or more of the firstinitial force reading and the first final force reading exceeds thethreshold force reading, an alarm sequence may be initiated on theinfusion pump assembly.

Determining the at least a second rate-of-change force reading mayinclude determining at least a second initial force reading prior todispensing the at least a second dose of the infusible fluid. The atleast a second dose of the infusible fluid may be dispensed. At least asecond final force reading may be determined subsequent to dispensingthe at least a second dose of the infusible fluid. The at least a secondrate-of-change force reading may be determined based, at least in part,upon the at least a second initial force reading and the at least asecond final force reading.

The infusion pump assembly may include a battery assembly configured topower the infusion pump assembly. An actual voltage level of the batteryassembly may be compared to a minimum voltage requirement to determineif the actual voltage level meets the minimum voltage requirement. Ifthe actual voltage level does not meet the minimum voltage requirement,an alarm sequence may be initiated on the infusion pump assembly.

One or more displaceable mechanical components included within theinfusion pump assembly may be monitored to determine if the one or moredisplaceable mechanical components were displaced an expecteddisplacement in response to delivery of one or more of the first dose ofthe infusible fluid and the second dose of the infusible fluid. If theone or more displaceable mechanical components were not displaced theexpected displacement in response to delivery of one or more of thefirst dose of the infusible fluid and the second dose of the infusiblefluid, an alarm sequence may be initiated on the infusion pump assembly.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will become apparent from the description, the drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an infusion pump assembly executing anocclusion detection process; and

FIG. 2 is a flowchart of the occlusion detection process of FIG. 1 .Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 , there is shown in infusion pump assembly 10 thatmay be configured to deliver infusible fluid 12 to user 14. As discussedabove, infusible fluid 12 may be delivered intravenously (i.e., into avein), subcutaneously (i.e., into the skin), arterially (i.e., into anartery), and epidurally (i.e., into the epidural space). Examples ofinfusible fluid 12 may include but are not limited to insulin,nutrients, saline solution, antibiotics, analgesics, anesthetics,hormones, vasoactive drugs, and chelation drugs.

Infusion pump assembly 10 may include processing logic 16 that executesone or more processes that may be required for infusion pump assembly 10to operate properly. An example of such a process may include but is notlimited to occlusion detection process 18, which will be discussed belowin greater detail. Processing logic 16 may include one or moremicroprocessors (not shown), one or more input/output controllers (notshown), and cache memory devices (not shown). One or more data busesand/or memory buses may be used to interconnect processing logic 16 withone or more subsystems.

Examples of such subsystems may include but are not limited to memorysystem 20, input system 22, display system 24, motor assembly 26, forcesensor 28, and displacement detection device 30. Infusion pump assembly10 may include a power source (e.g. battery assembly 32) for providingelectrical power to processing logic 16 and one or more of thesubsystems (e.g., memory system 20, input system 22, display system 24,motor assembly 26, force sensor 28, and displacement detection device30).

The instruction sets and subroutines of occlusion detection process 18,which may be stored on a storage device (e.g., memory system 20)accessible by processing logic 16, may be executed by one or moreprocessors (not shown) and one or more memory architectures (e.g.,memory system 20) included within infusion pump assembly 10. Examples ofmemory system 20 may include but are not limited to: a random accessmemory; a read-only memory; and a flash memory.

Infusion pump assembly 10 may include reservoir assembly 34 configuredto contain infusible fluid 12. In some embodiments, the reservoirassembly 34 may be a reservoir assembly similar to that described inU.S. Patent Application Publication No. US-2004-0135078-A1, publishedJul. 15, 2004, which is herein incorporated by reference in itsentirety. In other embodiments, the reservoir assembly may be anyassembly in which fluid may be acted upon such that at least a portionof the fluid may flow out of the reservoir assembly, for example, thereservoir assembly, in various embodiments, may include, but is notlimited to: a barrel with a plunger, a cassette or a container at leastpartially constructed of a flexible membrane.

Plunger assembly 36 may be configured to displace infusible fluid 12from reservoir assembly 34 through cannula assembly 38 so that infusiblefluid 12 may be delivered to user 14. In this particular embodiment,plunger assembly 36 is shown to be displaceable by partial nut assembly40, which may engage lead screw assembly 42 that may be rotatable bymotor assembly 26 in response to signals received from processing logic16. In this particular embodiment, the combination of motor assembly 26,plunger assembly 36, partial nut assembly 40, and lead screw assembly 42may form a pump assembly that effectuates the dispensing of infusiblefluid 12 contained within reservoir assembly 34. An example of partialnut assembly 40 may include but is not limited to a nut assembly that isconfigured to wrap around lead screw assembly 42 by e.g., 30 degrees. Insome embodiments, the pump assembly may be similar to one described inU.S. Pat. No. 7,306,578, issued Dec. 11, 2007, which is hereinincorporated by reference in its entirety.

During operation of infusion pump assembly 10, infusible fluid 12 may bedelivered to user 14 in accordance with e.g. a defined deliveryschedule. For illustrative purposes only, assume that infusion pumpassembly 10 is configured to provide 0.10 mL of infusible fluid 12 touser 14 every three minutes. Accordingly, every three minutes,processing logic 16 may provide the appropriate drive signals to motorassembly 26 to allow motor assembly 26 to rotate lead screw assembly 42the appropriate amount so that partial nut assembly 40 (and thereforeplunger assembly 36) may be displaced the appropriate amount in thedirection of arrow 44 so that 0.10 mL of infusible fluid 12 are providedto user 14 (via cannula 38).

As discussed above, processing logic 16 may execute occlusion detectionprocess 18, and occlusion detection process 18 may be configured tomonitor one or more events that are occurring within infusion pumpassembly 10 to determine whether or not an occlusion (e.g., a blockage)has occurred within e.g. cannula assembly 38.

Referring also to FIG. 2 , occlusion detection process 18 may determine100 a rate-of-change force reading (e.g., FR01) that corresponds to thedelivery of first dose 46 of infusible fluid 12.

When determining 100 the rate-of-change force reading (e.g., FR01),occlusion detection process 18 may determine 102 an initial forcereading prior to dispensing first dose 46 of infusible fluid 12. Asdiscussed above, infusion pump assembly 10 may regularly dispenseindividual doses of infusible fluid 12 based upon one or more infusionschedules. For example and as discussed above, infusion pump assembly 10may be configured to dispense 0.10 mL of infusible fluid 12 to user 14every three minutes.

When determining 102 the initial force reading prior to dispensing firstdose 46 of infusible fluid 12, occlusion detection process 18 may obtainthe initial force reading from force sensor 28. Force sensor 28 mayinclude one or more strain gauges and/or pressure sensing gauges and maybe positioned between motor assembly 26 and an immovable object (e.g.bracket assembly 48) included within infusion pump assembly 10.

In one embodiment, force sensor 28 includes four strain gauges (notshown), such that: two of the four strain gauges are configured to becompressed when driving plunger 36 into reservoir assembly 34; and twoof the four strain gauges are configured to be stretched when drivingplunger 36 into reservoir assembly 34. The four strain gauges (notshown) may be connected to a Wheatstone Bridge (not shown) that producesan analog force signal (not shown) that is a function of the pressuresensed by force sensor 28. The analog force signal (not shown) producedby force sensor 28 may be provided to an analog-to-digital converter(not shown) that may convert the analog force signal (not shown) into adigital force signal (not shown) that may be provided to processinglogic 16. An amplifier assembly (not shown) may be positioned prior tothe above-described analog-to-digital converter and may be configured toamplify the output of e.g., force sensor 28 to a level sufficient to beprocessed by the above-described analog-to-digital converter.

Provided that there is not an occlusion within e.g. cannula assembly 38,the initial force reading obtained by occlusion detection process 18prior to infusion pump assembly 10 dispensing first dose 46 of infusiblefluid 12 should be zero pounds. Once occlusion detection process 18determines 102 the initial force reading, infusion pump assembly 10 maydispense 104 first dose 46 of infusible fluid 12 to user 14 via cannulaassembly 38. While the system may be described above and/or below ashaving a force reading of zero pounds prior to and/or subsequent todispensing infusible fluid 12, this is for illustrative purposes only,as frictional forces and/or backpressure may result in force readingsthat are slightly higher than zero pounds.

Once infusion pump assembly 10 dispenses 104 first dose 46 of infusiblefluid 12 to user 14, occlusion detection process 18 may determine 106 afinal force reading subsequent to dispensing 104 first dose 46 ofinfusible fluid 12. For example, once infusion pump assembly 10 hascompletely dispensed 104 first dose 46 of infusible fluid 12 to user 14,occlusion detection process 18 may obtain the final force reading fromforce sensor 28 in a process similar to that used to obtain the initialforce reading from force sensor 28.

Occlusion detection process 18 may determine 100 the rate-of-changeforce reading (e.g., FR01) based, at least in part, upon the initialforce reading and the final force reading. For example, occlusiondetection process 18 may subtract the initial force reading from thefinal force reading to determine the net force change that occurredwhile dispensing (in this particular example) 0.10 mL of infusible fluid12. As discussed above, provided that there are no occlusions withine.g. cannula assembly 38, the initial force reading (obtained from forcesensor 28) should be zero and the final force reading (also obtainedfrom force sensor 28) should also be zero. Accordingly, therate-of-change force reading (e.g., FR01) determined 100 by occlusiondetection process 18 should also be zero.

While the system is described above as determining 106 a final forcereading subsequent to dispensing 104 first dose 46 of infusible fluid12, this final force reading may actually be based upon the initialforce reading that is taken for the next dose of infusible fluid 12.Accordingly, by allowing the initial force reading of the second dose ofinfusible fluid 12 to provide the data for the final force reading ofthe first dose of infusible fluid 12, the total number of force readingsmade may be reduced by 50%.

Once the rate-of-change force reading (e.g., FR01) is determined,occlusion detection process 18 may store the rate-of-change forcereading (e.g., FR01) within e.g., storage cell 50 of storage array 52.Storage array 52 may be configured as a FIFO (first in, first out)buffer. Storage array 50 may be configured to allow occlusion detectionprocess 18 to maintain a plurality of historical values for therate-of-change force readings (e.g., FR01) discussed above. A typicalembodiment of storage array 50 may include twenty or forty individualstorage cells. As will be discussed below in greater detail, occlusiondetection process 18 may process these historical values of therate-of-change force readings to determine an average rate-of-changeforce reading over a desired infusible fluid volume/number of infusioncycles. While storage array 52 is illustrated in FIG. 1 as being amulti-column storage array, this is for illustrative purposes only andis not intended to be a limitation of this disclosure. For example,storage array 52 may be a single column storage array in which only therate-of-change force readings are stored.

Motor assembly 26 may be configured as e.g., a brush-type DC electricmotor. Further, motor assembly 26 may include a reduction gear assembly(not shown) that e.g. requires motor assembly 26 to rotate e.g.,three-thousand revolutions for each revolution of lead screw assembly42, thus increasing the torque and resolution of motor assembly 26 by afactor of three-thousand.

As discussed above, occlusion detection process 18 may process thehistorical values of the rate-of-change force readings to determine anaverage rate-of-change force reading over a desired infusible fluidvolume/number of infusion cycles. For example, occlusion detectionprocess 18 may determine an average rate-of-change force reading overeach forty infusion cycles. Accordingly, occlusion detection process 18may determine 108 additional rate-of-change force readings, each ofwhich corresponds to the delivery of additional doses of infusible fluid12. For example and for illustrative purposes only, occlusion detectionprocess 18 may determine 108 thirty-nine additional rate-of-change forcereadings for the next thirty-nine infusion cycles. Each of thesethirty-nine rate-of-change force readings may be stored in a uniquestorage cell of storage array 52. Once storage array 52 is completelyfull (i.e. contains forty rate-of-change force readings), occlusiondetection process 18 may determine an average rate-of-change forcereading for the set of forty rate-of-change force readings. Once thisaverage rate-of-change force reading is determined, storage cell 52 maybe cleared and the process of gathering additional rate-of-change forcereadings may be repeated.

When determining additional rate-of-change force readings, occlusiondetection process 18 may determine 110 an initial force reading prior todispensing the additional dose (e.g., dose 54) of infusible fluid 12.Dose 54 of infusible fluid may then be dispensed 112 by infusion pumpassembly 10. Occlusion detection process 18 may determine 114 a finalforce reading subsequent to dispensing dose 54 of infusible fluid 12.

Occlusion detection process 18 may determine 108 the additionalrate-of-change force readings (e.g., FR2) based, at least in part, uponthe initial force reading and the final force reading for eachadditional dose of infusible fluid 12. As discussed above, provided thatthere are no occlusions within e.g. cannula assembly 38, the initialforce reading (obtained from force sensor 28) should be zero and thefinal force reading (also obtained from force sensor 28) should also bezero. Accordingly, the rate-of-change force reading (e.g., FR2)determined 108 by occlusion detection process 18 should also be zero. Asdiscussed above, once the additional rate-of-change force readings(e.g., FR2) are determined, occlusion detection process 18 may store therate-of-change force reading (e.g., FR2) within e.g., storage cell 56 ofstorage array 52.

Assume for illustrative purposes that occlusion detection process 18continues to calculate the rate-of-change force readings in the mannerdescribed above and continues to store these calculated rate-of-changeforce readings within storage array 52. Further, assume for illustrativepurposes that infusion pump assembly 10 continues to operate properly(i.e. without any occlusions) for the first thirty-three infusioncycles. Accordingly, the first thirty-three rate-of-change forcereadings (FR01-FR33) are all zero, as their respective initial forcereading and final force reading were all zero. However, assume forillustrative purposes that an occlusion (e.g. occlusion 58) occurswithin cannula assembly 38 prior to calculating the thirty-fourth,rate-of-change force reading (e.g., FR34), which is stored withinstorage cell 60. Assume for illustrative purposes that when determiningthe thirty-fourth rate-of-change force reading (e.g., FR34), occlusiondetection process 18 determines 110 an initial force reading of 0.00pounds. When infusion pump assembly 10 begins to dispense 112 thethirty-fourth dose of infusible fluid 12, as occlusion 58 is presentwithin cannula assembly 38, the fluid displaced from reservoir assembly34 by plunger assembly 36 will not be able to pass through cannulaassembly 38. Accordingly, the pressure within reservoir assembly 34 willbegin to build. Therefore, assume for illustrative purposes thatocclusion detection process 18 determines 114 a final force reading of0.50 pounds. Accordingly, occlusion detection process 18 may determine108 the rate-of-change force reading (e.g., FR34) to be 0.50 poundsminus 0.00 pounds, for a rate-of-change of 0.50 pounds.

Due to the presence of occlusion 58 within cannula assembly 38, whenmotor assembly 26 attempts to dispense the next dose of infusible fluid12, 0.50 pounds of pressure sensed by force sensor 28 will still bepresent within fluid reservoir 34. Accordingly, when determining thethirty-fifth rate-of-change force reading (e.g., FR35), the initialforce reading determined 110 by occlusion detection process 18 may bethe same as the final force reading determined by occlusion detectionprocess 18 when determining the thirty-fourth rate-of-change forcereading (e.g., FR34).

Occlusion detection process 18 may determine 116 an averagerate-of-change force reading (e.g., AFR) based, at least in part, uponall or a portion of the rate-of-change force readings included withinstorage array 52. Assume for illustrative purposes that occlusiondetection process 18 is configured to consider all rate-of-change forcereadings (e.g., FR01-FR40) included within storage array 52.Accordingly, occlusion detection process 18 may calculate themathematical average of all rate-of-change force readings (e.g.,FR01-FR40) included within storage array 52. In this particular example,average rate-of-change force reading (e.g., AFR) has a mathematicalvalue of 0.105 pounds. While the system is described above as beingcapable of considering all rate-of-change force readings (e.g.,FR01-FR40) included within storage array 52, this is for illustrativepurposes only and is not intended to be a limitation of this disclosure,as other configurations are possible. For example, occlusion detectionprocess 18 may be configured to determine 116 an average rate-of-changeforce reading (e.g., AFR) once storage array 52 is populated with e.g.,the first five rate-of-change force readings. If determining 116 anaverage rate-of-change force reading (e.g., AFR) prior to storage array52 being completely populated, any unpopulated rows within storage array52 may be populated with zeros.

Occlusion detection process 18 may compare 118 the averagerate-of-change force reading (e.g., AFR) to a threshold rate-of-changeforce reading to determine if the average rate-of-change force reading(e.g., AFR) exceeds the threshold rate-of-change force reading. If theaverage rate-of-change force reading does not exceed the thresholdrate-of-change force reading, infusion pump assembly 10 may continue 120to operate normally. However, if the average rate-of-change forcereading exceeds the threshold rate-of-change force reading, an alarmsequence may be initiated 122 on infusion pump assembly 10. For example,assuming for illustrative purposes that occlusion detection process 18is configured to have a threshold rate-of-change force reading of 0.90pounds, only after the average rate-of-change force reading (e.g., AFR)exceeds 0.90 pounds will the alarm sequence be initiated 120. Thus, inthese embodiments, measuring the rate-of-change may ensure alarmsequences are triggered more reliably when actual occlusions haveoccurred. As described below, user 14, in some embodiments, may definethe sensitivity of the system.

The sensitivity of occlusion detection process 18 may be based upon auser-defined sensitivity setting selected 124 by e.g., user 14. Forexample, assume that occlusion detection process 18 has two sensitivitysettings, namely a high sensitivity setting and a low sensitivitysetting. Further, assume that each of the sensitivity settings isassociated with a unique manner of determining the rate-of-change forcereadings included within storage array 52. As discussed above, occlusiondetection process 18 is described above as determining 100 arate-of-change force reading (e.g., FR01) that corresponds to thedelivery of first dose 46 of infusible fluid 12. Assume that whenconfigured in the high sensitivity setting, occlusion detection process18 may determine 100 a rate-of-change force reading that corresponds tothe delivery of a comparitively smaller quantity of infusible fluid 12.Further, assume that when configured in the low sensitivity setting,occlusion detection process 18 may determine 100 a rate-of-change forcereading that corresponds to the delivery of a comparitively largerquantity of infusible fluid 12. For example, assume that when in thehigh sensitivity setting, occlusion detection process 18 determines 100a rate-of-change force reading that corresponds to the delivery of 0.10mL of infusible fluid 12. Further, assume that when in the lowsensitivity setting, occlusion detection process 18 determines 100 arate-of-change force reading that corresponds to the delivery of a 0.20mL dose 46 of infusible fluid 12. Accordingly, when placed in the highsensitity setting, additional measurements are taken and occlusiondetection process 18 is more responsive. However, false alarms may occurmore frequently. Conversely, when placed in the low sensitity setting,fewer measurements are taken and occlusion detection process 18 is lessresponsive. However, false alarms may occur less frequently due to the“averaging” effect of taking fewer measurements. Accordingly, in orderto avoid nuisance alarms (or to reduce the number of alarms), the user(e.g. user 14) may select 124 the low sensitivity setting.

The alarm sequence initiated 122 may include any combination ofvisual-based (via display system 24), audible-based (via a speakerassembly, not shown), and vibration-based alarms (via a vibrationassembly, not shown). User 14 may be able to select between thehigh-sensitivity setting and the low-sensitivity setting via one or moreof input system 22 and display system 24.

While infusion pump assembly 10 is described above as delivering aplurality of identically-sized doses of infusible fluid 12 andcalculating a rate-of-change force reading (e.g., FR01) for each dose ofinfusible fluid 12, this is for illustrative purposes only and is notintended to be a limitation of this disclosure. Specifically, infusionpump assembly 10 may be configured to provide non-identical doses ofinfusible fluid 12. Further, infusion pump assembly 10 may be configuredto allow user 14 to manually administer a “bolus” dose of infusiblefluid 12 in a size determined by user 14. Accordingly, occlusiondetection system 18 may be configured to monitor the volume of infusiblefluid 12 dispensed in each dose and may be configured to populatestorage array 52 so that each rate-of-change force reading (e.g., FR01)included within storage array 52 is indicative of the rate-of-changeforce sensed by occlusion detection process 18 when dispensing anequivalent quantity of infusible fluid 12. Accordingly, occlusiondetection system 18 may be configured to “normalize” the rate-of-changeforce readings determined based upon the quantity of infusible fluiddelivered.

For example, assume that occlusion detection system 18 is configured sothat a storage cell included within storage array 52 is populated eachtime 0.10 mL of infusible fluid 12 is dispensed. Assume for illustrativepurposes only that user 14 decides to dispense a 0.25 mL dose ofinfusible fluid 12. As the 0.25 mL dose of infusible fluid 12 is greaterthan the 0.10 mL increments at which occlusion detection process 18 isconfigured to populate storage array 52, occlusion detection process 18may record multiple entries (and, therefore, populate multiple storagecells) within storage array 52 for the single 0.25 mL dose of infusiblefluid 12.

Specifically, assume that the initial force reading determined 110 priorto delivering the 0.25 mL dose of infusible fluid 12 is 0.00 pounds andthe final force reading determined 114 after dispensing 112 the 0.25 mLdose of infusible fluid 12 is 1.00 pounds. As the 0.25 mL dose ofinfusible fluid 12 is two-and-a-half times the 0.10 mL increments inwhich occlusion detection process 18 is configured to populate storagearray 52, occlusion detection process 18 may “normalize” thisrate-of-change force reading. Specifically, occlusion detection process18 may divide 1.00 pounds by 0.25 mL to determine that the force changed0.40 pounds per 0.10 mL. Accordingly, occlusion detection process 18 maycalculate a rate-of-change force reading of 0.40 pounds for the first0.10 mL dose of infusible fluid 12, 0.40 pounds for the second 0.10 mLdose of infusible fluid 12, and 0.20 pounds for the last 0.05 mL dose ofinfusible fluid 12.

Accordingly, occlusion detection process 18 may populate storage array52 so that a first storage cell (associated with the first 0.10 mL doseof infusible fluid 12) defines an initial force reading of 0.00 pounds,a final force reading of 0.40 pounds and a rate-of-change force readingof 0.40 pounds. Further, occlusion detection process 18 may populatestorage array 52 so that a second storage cell (associated with thefirst 0.10 mL dose of infusible fluid 12) defines an additional forcereading of 0.40 pounds, a final force reading of 0.80 pounds and arate-of-change force reading of 0.40 pounds.

Concerning the remaining 0.05 mL of the 0.25 mL dose of infusible fluid12, as this is less than the 0.10 mL increment at which occlusiondetection process 18 is configured to populate storage array 52, thenext cell within storage array 52 will not be populated until anadditional 0.05 mL dose of infusible fluid 12 is dispensed.

Continuing with the above-stated example, assume for illustrativepurposes that infusion pump assembly 10 administers a 0.15 mL dose ofinfusible fluid 12. Occlusion detection process 18 may combine the first0.05 mL of the 0.15 mL dose of infusible fluid 12 with the remaining0.05 mL of the 0.25 mL dose of infusible fluid 12 to form a complete0.10 mL increment for recording within storage array 52.

Again, occlusion detection process 18 may “normalize” the 0.15 mL doseof infusible fluid 12. Assume for illustrative purposes that whendispensing the 0.15 mL of infusible fluid 12, occlusion detectionprocess 18 determines an initial force reading of 1.00 pounds and afinal force reading of 1.60 pounds. In the manner described above,occlusion detection process 18 may divide 0.60 pounds (i.e., 1.60 poundsminus 1.00 pounds) by 0.15 mL to determine that the force changed 0.40pounds per 0.10 mL. Accordingly, occlusion detection process 18 maycalculate a rate-of-change force reading of 0.20 pounds for the first0.05 mL of the 0.15 mL dose of infusible fluid 12, and 0.40 pounds forthe remaining 0.10 mL of the 0.15 mL dose of infusible fluid 12.

Accordingly, occlusion detection process 18 may populate storage array52 so that a third storage cell (associated with the combination of thefirst 0.05 mL of the 0.15 mL dose of infusible fluid 12 with theremaining 0.05 mL of the 0.25 mL dose of infusible fluid 12) defines aninitial force reading of 0.80 pounds (i.e., which is the final forcereading after the second 0.10 mL of the 0.25 mL dose of infusible fluid12), a final force reading of 1.20 pounds (i.e., the sum of the initialforce reading of 1.00 pounds plus the 0.20 pound offset for the first0.05 mL of the 0.15 mL dose of infusible fluid 12) and a rate-of-changeforce reading of 0.40 pounds. Further, occlusion detection process 18may populate storage array 52 so that a fourth storage cell (associatedwith the last 0.10 mL of the 0.15 mL dose of infusible fluid 12) definesan initial force reading of 1.20 pounds, a final force reading of 1.60pounds and a rate-of-change force reading of 0.40 pounds.

In addition to comparing 118 the average rate-of-change force reading(e.g., AFR) to a threshold rate-of-change force reading to determine ifthe average rate-of-change force reading (e.g., AFR) exceeds thethreshold rate-of-change force reading, occlusion detection process 18may compare 126 one or more of the initial force reading and the finalforce reading to a threshold force reading to determine if either theinitial force reading or the final force reading exceeds the thresholdforce reading. If either of the initial force reading or the final forcereading exceeds the threshold force reading, an alarm sequence may beinitiated 128 on infusion pump assembly 10.

For example, occlusion detection process 18 may define a threshold forcereading, which if exceeded by either the initial force reading (which isdetermined prior to dispensing a dose of infusible fluid 12) or thefinal force reading (which is determined after dispensing a dose ofinfusible fluid 12), an occlusion is deemed to be occurring. Example ofsuch a threshold force reading is 4.00 pounds. Therefore, if afterdispensing a dose of infusible fluid 12, occlusion detection process 18determines a final force reading of 5.20 pounds, occlusion detectionprocess 18 may initiate 128 an alarm sequence, as 5.20 pounds exceedsthe 4.00 threshold force reading. The alarm sequence initiated 128 mayinclude any combination of visual-based (via display system 24),audible-based (via a speaker assembly, not shown), and vibration-basedalarms (via a vibration assembly, not shown).

As discussed above, infusion pump assembly 10 may include batteryassembly 32 configured to power infusion pump assembly 10. Before and/orafter dispensing a dose of infusible fluid 12, occlusion detectionprocess 18 may compare 130 the actual voltage level of battery assembly32 to a minimum voltage requirement to determine if the actual voltagelevel of battery assembly 32 meets the minimum voltage requirement. Ifthe actual voltage level does not meet the minimum voltage requirement,occlusion detection process 18 may initiate 132 an alarm sequence oninfusion pump assembly 10. The alarm sequence initiated 132 may includeany combination of visual-based (via display system 24), audible-based(via a speaker assembly, not shown), and vibration-based alarms (via avibration assembly, not shown). For example, assume for illustrativepurposes that battery assembly 32 is a 5.00 VDC battery assembly.Further, assume that the minimum voltage requirement is 3.75 VDC (i.e.,75% of normal voltage). Accordingly, if occlusion detection process 18determines 130 that the actual voltage level of battery assembly 32 is3.60 VDC, occlusion detection process 18 may initiate 132 an alarmsequence on infusion pump assembly 10.

Additionally, occlusion detection process 18 may monitor one or more ofthe displaceable mechanical components included within infusion pumpassembly 10 to determine 134 if one or more displaceable mechanicalcomponents included within infusion pump assembly 10 were displaced anexpected displacement in response to delivering a dose of infusiblefluid 12. If the displaceable mechanical components monitored were notdisplaced the expected displacement in response to delivering a dose ofinfusible fluid 12, occlusion detection process 18 may initiate 136 analarm sequence on infusion pump assembly 10. The alarm sequenceinitiated 134 may include any combination of visual-based (via displaysystem 24), audible-based (via a speaker assembly, not shown), andvibration-based alarms (via a vibration assembly, not shown).

For example, upon processing logic 16 energizing motor assembly 26 todispense 0.10 mL of infusible fluid 12, occlusion detection process 18may (via displacement detection device 30) confirm that partial nutassembly 40 did indeed move the expected displacement. Accordingly, inthe event that partial nut assembly 40 does not move the expecteddisplacement, a mechanical failure (e.g. the failure of partial nutassembly 40, the failure of lead screw assembly 42, the failure of motorassembly 26) may have occurred. In the event that the expecteddisplacement of partial nut assembly 40 cannot be confirmed, occlusiondetection process 18 may initiate 136 alarm sequence on infusion pumpassembly 10.

When determining whether partial nut assembly 40 was displaced theexpected amount, tolerances may be utilized. For example. assume that todeliver a 0.10 mL dose of infusible fluid 12, occlusion detectionprocess 18 may expect to see partial nut assembly 40 displaced 0.050inches. Accordingly, occlusion detection process 10 may utilize a 10%error window in which movement of partial nut assembly 40 of less than0.045 inches (i.e., 10% less than expected) would result in occlusiondetection process 18 initiating 136 alarm sequence on infusion pumpassembly 10.

In one embodiment of displacement detection device 30, displacementdetection device 30 includes one or more light sources (not shown)positioned on one side of partial nut assembly 40 and one or more lightdetectors (not shown) positioned on the other side of partial nutassembly 40. Partial nut assembly 40 may include one or more passages(not shown) through which the light from the one or more light sources(not shown) included within displacement detection device 30 may shineand may be detected by the one or more light detectors (not shown)included within displacement detection device 30.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

What is claimed is:
 1. An infusion pump assembly comprising: a controlsystem to deliver doses of an infusible fluid of a first volume and asecond volume, wherein the first volume and second volume are not thesame, the control system configured to: determine a first volume initialforce reading prior to dispensing a dose of the first volume of theinfusible fluid; dispense a dose of the first volume of the infusiblefluid; determine a first volume final force reading subsequent todispensing a dose of the first volume of the infusible fluid; determinea first volume rate-of-change reading that corresponds to the deliveryof the first dose of the infusible fluid via an infusion pump assemblyby subtracting the first volume initial force reading from the firstvolume final force reading value; determine a second volume initialforce reading prior to dispensing a dose of the second volume of theinfusible fluid; dispense a dose of the second volume of the infusiblefluid; determine a second volume final force reading subsequent todispensing a dose of the second volume of the infusible fluid; determinea second volume rate-of-change reading that corresponds to the deliveryof the second dose of the infusible fluid via an infusion pump assemblyby subtracting the second volume initial force reading from the secondvolume final force reading value; compare the first volumerate-of-change reading to a first volume rate-of-change threshold todetermine if the first volume rate-of-change reading exceeds the firstvolume rate-of-change threshold; if the first volume rate-of-changereading exceeds the first volume rate-of-change threshold, initiate analarm on the infusion pump assembly; compare the second volumerate-of-change reading to a second volume rate-of-change threshold todetermine if the second volume rate-of-change reading exceeds the secondvolume rate-of-change threshold; and if the second volume rate-of-changereading exceeds the second volume rate-of-change threshold, initiate analarm on the infusion pump assembly.
 2. The infusion pump assembly ofclaim 1 wherein the control system determines the first volume rate ofchange reading by averaging a first volume rate of change from aplurality of doses of the first volume.
 3. The infusion pump assembly ofclaim 2 wherein the control system determines the second volume rate ofchange reading by averaging a second volume rate of change from aplurality of doses of the second volume.
 4. The infusion pump assemblyof claim 1 wherein the control system determines the second volume rateof change reading by averaging a second volume rate of change from aplurality of doses of the second volume.
 5. The infusion pump assemblyof claim 1 wherein the controller is configured to allow a user to setthe first volume rate of change threshold.
 6. The infusion pump assemblyof claim 1 wherein the controller is configured to allow the used to setthe first volume rate of change threshold and the second volume rate ofchange threshold.
 7. The infusion pump assembly of claim 1 wherein theinfusion pump assembly includes a battery assembly configured to powerthe infusion pump assembly, the control system further configured to:compare an actual voltage level of the battery assembly to a minimumvoltage requirement to determine if the actual voltage level meets theminimum voltage requirement; and if the actual voltage level does notmeet the minimum voltage requirement, initiate an alarm on the infusionpump assembly.
 8. An infusion pump assembly comprising: a control systemconfigured to allow a user to set and change a threshold for an alarm:monitor a displacement of a displaceable mechanical component includedwithin the infusion pump assembly; determine if the displaceablemechanical component was displaced an expected displacement in responseto delivery of one of a first dose of an infusible fluid and a seconddose of the infusible fluid by comparing the monitored displacement tothe expected displacement; determine an initial force reading from aforce sensor prior to dispensing the first dose and the second dose ofthe infusible fluid; determine a final force reading from the forcesensor after dispensing the first dose and the second dose of theinfusible fluid; compare, to the threshold, of the initial force readingor the final force reading to determine if the initial force reading orthe final force reading exceeds the threshold; and if the initial forcereading or final force reading exceeds the threshold, initiate an alarmon the infusion pump assembly.
 9. The infusion pump assembly of claim 8wherein the control system further configured to: determine a firstinitial force reading prior to dispensing the first dose of theinfusible fluid; dispense the first dose of the infusible fluid; monitora volume of the infusible fluid dispensed in the first dose; determine asecond initial force reading prior to dispensing the second dose of theinfusible fluid; set a first final force reading value as being equal tothe second initial force reading; dispense the second dose of theinfusible fluid; monitor a volume of the infusible fluid dispensed inthe second dose; determine a second final force reading subsequent todispensing the second dose of the infusible fluid; determine a firstrate-of-change reading that corresponds to the delivery of the firstdose of the infusible fluid via an infusion pump assembly by subtractingthe first initial force reading from the first final force readingvalue; determine at least a second rate-of-change reading thatcorresponds to the delivery of the second dose of the infusible fluidvia the infusion pump assembly by subtracting the second initial forcereading from the second final force reading; normalize the firstrate-of-change reading and the second rate-of-change reading to beindicative of the rates-of-change sensed for an equivalent quantity ofinfusible fluid; and determine an average rate-of-change reading based,at least in part upon the normalized first rate-of-change reading andthe normalized at least a second rate-of-change reading.
 10. Theinfusion pump assembly of claim 9 further configured to: compare theaverage rate-of-change reading to a threshold rate-of-change reading todetermine if the average rate-of-change reading exceeds the thresholdrate-of-change reading; and if the average rate-of-change readingexceeds the threshold rate-of-change reading, initiate an alarm on theinfusion pump assembly.
 11. The infusion pump assembly of claim 8wherein the infusion pump assembly includes a battery assemblyconfigured to power the infusion pump assembly, the control systemfurther configured to: compare an actual voltage level of the batteryassembly to a minimum voltage requirement to determine if the actualvoltage level meets the minimum voltage requirement; and if the actualvoltage level does not meet the minimum voltage requirement, initiate analarm on the infusion pump assembly.